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Instrument source
Coordinate quality
Manage...\Data
The instrument source describes where the coordinate triplet was measured or entered. The
options are GPS, TPS, LGO or Level.
Description
The Coordinate Quality is
•
computed on the rover for code solutions and phase fixed solutions.
•
an indicator for the quality of the observations.
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an indicator for the current satellite constellation.
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an indicator for different environmental conditions.
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derived such that there is at least a two third probability that the computed position devi-
ates from the true position by less than the CQ value.
•
different from the standard deviation.
CQ versus standard deviation
The standard deviation as CQ would often be too optimistic. This is why the computation of
the CQ in GPS1200+ is not simply based on the basic standard deviation algorithms.
For the standard deviation, there is, statistically, a 39.3 % probability in 2D that the computed
position deviates from the true position by less than the standard deviation. This is not
enough for a reliable quality indicator.
This is particularly true for low redundancy situations such as a constellation of four satellites.
In such a case the RMS converges to zero and the standard deviation would show an unre-
alistically small value.
GPS1200+
167
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